Electro-thermostatic appliances



April 28, 1959 H; e. RUIZ 2,884,502

' ELECTRO-THERMOSTATIC APPLIANCES 7 Filed May 24, 1957 0 (m INVENTOR HG u 112 ATroRNEYs United States Patent ELECTRO-THERMOSTATIC APPLIANCES Honorato Gutierrez Ruiz, Mexico City, Mexico Application May 24, 1957, Serial No. 661,422

1 Claim. (Cl. 200-122) It is well known that in electric circuits fuses are interposed in the circuit to prevent overloading the circuit, or to break the circuit in the event of an overload. While the fuses accomplish the purpose intended, their replacement is necessary when they blow out.

It is an object of this invention to provide an improved circuit breaking device which will effectively open the electric circuit when an overload or short circuit occurs, as well as to re-establish the circuit once the overload or short circuit is eliminated.

Another object of this invention is to provide an improved circuit breaking means which can be eifectively and accurately adjusted to bring about the results desired as described above.

A further object of this invention is to provide an improved circuit breaking means which will prevent fire hazards due to a circuit overload or to a short circuit.

A still further object of this invention is to provide a circuit breaking means embodied in an evacuated glass bulb instead of in a bulb filled with an inert gas in accordance with current practices.

In one of the embodiments of this invention described and illustrated herein, the electro-thermostatic switch is disposed in an evacuated glass bulb. The heat resisting properties of tungsten are utilized as the circuit breaking means, the heating of the bimetallic bars not being effected by the filament heat but brought about through the heating of a resistance member positioned intermediate the two bimetallic bars, the elements being connected in a series electric circuit and to a tungsten filament, to obtain more quickly a more effective heating of the bimetallric bars in order to increase the speed of the operation of the appliance. The function of the tungsten filament is reduced to the lending of its high resistance in short circuit cases.

Other and further objects and advantages of the present invention will become more obvious from a consideration of the following specification when read in conjunction with the annexed drawings, in which:

Figure l is a detailed side elevational view partly broken away of a thermostatic appliance constructed in accordance with one embodiment of this invention;

Figure 2 is a diagrammatic view of the appliance interposed in an electric circuit;

Figure 3 is a detailed side elevational view, partly in cross section, and illustrating a second embodiment of this invention; and,

Figure 4 is a diagrammatic view of an electric circu1t wherein the appliance illustrated in Figure 3 is interposed.

Referring now more specifically to the drawings, reference numeral designates, in general, an evacuated glass bulb having a threaded metallic plug 12 at one end thereof, the plug 12 being provided with a center tap 14. As is seen in Figure 1, the center contact 14 is insulated from the plug 12 by means of a plurality of dielectric members 16. A pair of bimetallic members 18 and 20 are disposed within the bulb 10 and the lower end of 2,884,502 Patented Apr. 28, 1959 these members are secured to a central supporting member 22 disposed within the bulb 10. The bimetallic members 18, 20 are mechanically connected together adjacent their lower ends by means of a spacer element 24 formed of a dielectric material. A resistance heating element 26 is disposed between the bimetallic members 18, 20 having one of its ends electrically connected at 44 to the bimetalmember 20. The other end of the resistance heating element 26 connects through a rigid supporting wire 30 with the metallic plug 12 at 32. A tungsten filament 34 surrounds the bimetallic members 18, 20 and one end of the filament 34 is connected through wire 36 with the center post 14. The other end of the filament 34 is connected at 28 to the bimetallic member 18.

The upper end of the bimetallic member 18 has fixedly secured thereto a switch contact point 37 and the upper end of the bimetallic member 20 has mounted thereon a switch contact 38 which is adjustable towards and away from the switch contact 37 by means of a screw 40.

A large capacity resistance 42 has its opposite ends respectively connected with the bimetallic member 18 at 28 and with the bimetallic member 20 at 44.

The values of the filament 34 are carefully calculated so that during the normal operation of the appliance in an electrical circuit the normal voltage and current of the circuit will not heat the filament 34 or resistance heating element 26 to effect a flexing of the bimetallic members 18-2il away from each other.

As is seen in Figure 2 of the drawings, the appliance described above is adapted to be threaded into a socket (not shown) which is connected with one side of an electric circuit including the supply leads 46, 48, and is connected in series in the circuit. In the drawing, reference numeral 50 designates a motor or other device to which this appliance is connected. As illustrated in Figure 2 current flows through the filament 34 and is conducted through the bimetallic member 18, switch contact 37, switch contact 38, the bimetallic member 20, to the resistance heating element 26. The current leaves the other side of the resistance heating element 26 and passes to one side of the motor 50. The other side of the motor 50 is connected with the other side of the line through lead 48. From the foregoing description it is now apparent that the filament 34, bimetallic members 18, 20, contact members 37, 38, and the resistance heating element 26 are all in series with the motor 50. Also from Figure 2 of the drawings it is seen that the tungsten member 42 is connected in parallel across the bimetallic members 18, 20.

During the normal operation of the above described series circuit very little current flows through the filament 42 as it is short circuited by the filament 34, the bimetallic members 18, 20 and the resistance heating element 26. When short circuits occur the element 26 heats causing the bimetallic members 18-20 to separate. On overloading of the circuit the current flow through the filament 42 causes the same to heat up due to its great high resistance and to eifect a voltage drop which is unobtainable in the series circuit. The heated filament 42 causes the bimetallic members 18, 20 to remain apart from each other to efiect a prolonged separation of the contacts 37, 38. The separation of the contacts 37, 38 is maintained until the overload or short circuit is removed and the filament 42 cools off.

In the above described circuit, the filament 42 absorbs the rupturing spark of the circuit thus producing a break in the circuit on each occurrence of the rupturing spark. This gives rise to greater safety for the filaments and the contacts, and for the appliance itself.

As a modified form of this invention, it has been found feasible to omit the shunting filament 42. In this instance, the current travels in a series circuit through wire 46, the filament 34, bimetallic member 18, switch contact 37, switch contact 38, the bimetallic member 20, and through the resistor 26 to one side of the motor 50. The other side of the motor 50 is, as before, tied to the other side of the line 48. Under these conditions, and should the circuit be overloaded the resistance 26 generates heat which causes the bimetallic members 18, 2th to move away from each other to separate the switch points 37, 38 and consequently interrupt the circuit. As soon as the bimetallic members 18-20 and the resistance member 26 has cooled sufliciently to permit the contacts 37, 38 to reengage, the circuit is reestablished if the overload or short circuit has been removed. If it has not, the circuit resistance 26 again heats and breaks the contact between the points 37 and 38 in the manner ascribed.

Another embodiment of this invention is illustrated in Figures 3 and 4. In this embodiment, the appliance comprises an evacuated bulb 51 having a threaded metallic base 52 fixedly secured to one end thereof. A relatively stifi supporting wire 53 has one of its ends disposed within the bulb 51 and which is connected with one end of a high resistance tungsten filament 54. The other end of the wire 53 extends inwardly into the base 52 and is connected with a center post 56. The other end of the filament 54 is electrically connected at 58 with a second relatively rigid wire 60 the other end of which is electrically connected at 62 with one side of a resistance 64. As is seen in Figure 3, the wires 52 and 60 extend through dielectric base 66.

The other side of the resistance 64 extends through a cylindrical wall 68 and is electrically connected at 70 to the metallic base 52.

A support 72 is fixedly connected to the wall 68 and pivotally connects at 74 one end of a bimetallic element 76. The other end of the bimetallic element 76 is pivoted at 78 to one end of a link 80, the other end of the link 80 being pivotally connected at 82 to the housing of a mercury switch 84. The mercury switch 84 is pivotally mounted at 86 on the cylindrical wall 68. A socket (not shown) receives the plug 52 and the socket is connected in series with the motor 94.

During the normal operation of this embodiment of the invention current flows through the wire 83 through the resistor 64, the mercury switch contacts 90, 92, the filament 54 and thence to one side of the motor 94. The other side of the motor 94 is connected to the other side of the line 96.

Should the circuit become overloaded, the resistance 64 becomes heated and causes the bimetallic bar 76 to flex and thereby actuate the mercury switch 84 to open the switch contact points 90, 92. 'Thus the circuit is broken. Upon the cooling of the bimetallic bar 76 and of the resistance member 64, the mercury switch is pivoted to close the contacts 90, 92 and reestablish the circuit to the motor 94.

While the resistance 64, the lever 76 and switch 84 are shown as being housed in the base 52, these elements may be encased in a suitable separate housing (not shown).

Having thus described the preferred embodiments of the invention, it should be understood that numerous modifications and structural adaptations may be resorted to without departing from the scope of the appended claim.

What is claimed is:

A thermostatic circuit making and breaking switch comprising an evacuated hollow bulb having an internally projecting support, a pair of spaced substantially parallel bimetallic elements each having one of their respective ends fixedly secured to said support, a switch contact member on each of the other ends of said bimetallic elements, said contact members normally being in engagement with each other, a heating element comprising an electrical resistance supported in heat exchange relation closely adjacent to and intermediate said bimetallic elements and extending longitudinally thereof, a resistance filament in said bulb supported in heat exchange relation closely adjacent to and surrounding said bimetallic elements, said bimetallic elements, said electrical resistance and said resistance filament being connected in series, means for connecting said series connected elements in series with a load carrying electric circuit whereby an overload or short circuit of said load carrying circuits causes said electrical resistance to become heated and the heat therefrom heats said bimetallic elements and efiects a flexing of said bimetallic elements to separate said switch contact members, thereby opening said series circuit, and a heavy capacity high resistance element disposed in said bulb, said last-named resistance element being shunt connected across said bimetallic elements and being adapted to maintain said contact members separated on prolonged overload conditions in said circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,838,372 De Castro Dec. 29, 1931 2,727,960 Ruiz Dec. 20, 1955 FOREIGN PATENTS 697,720 Germany Oct. 22, 1940 720,777 France Dec. 12, 1931 

